1. Field of the Invention
This invention relates to an adhesive tape, more particularly to an adhesive tape which can be suitably used for adhering materials having large stretchability such as vulcanized rubber to each other.
2. Related Art Statement
Sporting goods, such as a wet suit or a dry suit, made of rubber have been prepared by cutting raw sheet of vulcanized rubber to a predetermined shape and then sewing cut pieces with each other. Also, in the case where very high airtight property or waterproof property is required, after sewing the cut pieces, sewed portions are then further sealed with an adhesive and the like. However, the above procedure of sewing or sealing requires much labor so that a production cost of the sporting goods increases. Therefore, in recent years, technique wherein cut pieces are not sewed but adhered by using an adhesive tape has been utilized. As an adhesive to be used in this kind of adhesive tapes, there have been known a chloroprene type adhesive, to which a curing agent such as isocyanate is added; an isocyanate type adhesive; a hot melt type adhesive; and the like.
However, vulcanized rubber has a disadvantage that it is usually poor in adhesiveness for those conventional adhesive tapes. This is because additives included in vulcanized rubber such as stearic acid, wax or an antioxidant are gradually migrated to the surface layer thereof whereby adhesive force of the adhesive is decreased. Further, stretchability of the adhesive is poor so that it cannot follow to stretching or bending of vulcanized rubber. Thus, in the case of sporting goods made of rubber which has particularly high stretchability, such as a wet suit or a dry suit, adhesive surface becomes gradually aged and cracks are generated. And thus, there is a problem that water penetrates through adhered portion whereby lifetime of the product becomes markedly short. From the above circumstances, there have been desired to provide an adhesive tape having firm adhesion to vulcanized rubber as well as high elasticity of a coated film.